DESCRIPTION:
This is an example of a “Pritchard model” microscope, which is unsigned. The presence of the Turrell stage suggests that it dates from after 1834.

The instrument is supported by a tripod foot, the legs being of equal proportions, unlike most examples signed by Pritchard himself, which have an asymmetrical configuration. From this arises a central 110 mm tall brass pillar which extends into a compass joint which can be tightened. Its central portion ends in a clamp which encircles the limb, and can be tightened with a large knurled knob. This allows for rotation of the entire body of the microscope through 90° in both directions for use with a vial holder which can be affixed to a lug with two brass pins in lieu of the stage.

The classical Turrell stage is of the type first described, and features U-shaped sliding stage clips and concentric controls for the X and Y axis stage movements. Attached to its under surface is a cylindrical screw-in attachment with a wheel of aperture stops.

The tailpiece is an extension of the limb and carries a sleeve for the single-sided concave mirror. The upper end of the limb contains a triangular bar with rack and pinion coarse adjustment which is operated by two knurled heads. There is no fine adjustment. The horizontal arm is double sided but on this example, unlike some signed Pritchard examples, there is no provision for use as a simple microscope. Instead, a single threaded aperture takes the 185 mm long body tube with an internal diameter of 33.2 mm for the eye piece.

ACCESSORIES:

EYEPIECES:
There is a single top hat eye piece with an approximate magnification of x5.

OBJECTIVES:
When acquired, this microscope came with a single objective with protective screwcaps and Pritchard pre-RMS thread, with an approximate focal length of ½ inch. The present owner has added a set of Chevalier-type French button objectives contained in a morocco covered box lined with dark red velvet, which have the same female thread.

Optical data for these obtained with stage micrometre and Cheshire apertometer:

Objective	n.a.	Magnification with eyepiece
1/2 In	0.17	85
No 3	0.38	180
Unmarked	0.40	270
No 5	0.56	290

STAGE ACCESSORIES:
These include stage forceps, a Pritchard-type live box, and a bulls eye condenser on a stand. Shown on the microscope to the left is a replica vial holder created by the present owner.

CASE:
The microscope is stored in its original attractive rosewood cabinet measuring 280 mm (H)x 325 mm (W)x 203 mm (D) with glass panelled front door. The body tube and all accessories are stored in a large bottom drawer. The microscope body slides into a central recess flanked by a row of 6 drawers on each side which have turned and numbered bone knobs. These contain a selection of standard 1 x 3 inch slides, many retailed by J. Wellington of Cheltenham.